Monera are bacteria an other mostly tiny, single-celled organisms whose genetic material is loose in the cell. The genetic material of plants, animals, and other eukaryotes (true nucleus), on the other hand, is held in the cell's nucleus. While the Monera were briefly understood to be one of five biological kingdoms, it is now understood to comprise two kingdoms: the eubacteria and the archaebacteria. The Monera kingdom included most organisms with a prokaryotic cell organization (that is, no nucleus). For this reason, the kingdom was sometimes called Prokaryota or Prokaryotae.